Lapidary machine

ABSTRACT

A lapidary machine adapted to produce cabochon shaped gem stones or the like; the machine having a powered rotary grinding wheel provided with a contoured in cross section annular grinding surface adapted to grind peripheries of cabochon shaped gem stones; a powered rotary dop holding shaft structure adapted rotatably to carry a dop supported gem stone in contact with said annular grinding surface; said shaft structure axially parallel to and laterally movable relative to the rotary axis of said grinding wheel, said shaft structure having a generally oval shaped cam thereon; a normally stationary idler roller having a periphery engagable by said cam and means for adjusting the position of the periphery of said idler roller in directions laterally relative to the rotary axis of said shaft structure in order to progressively cut peripheries of stones down and to produce cabochon shaped stones of various overall sizes.

United States Patent Colbaugh 1 July4, 1972 [541 LAPIDARY MACHINE Syril A. Colbaugh, Chloride Star Route 93, PO. Box 210, Kingman, Ariz. 86401 [22] Filed: Oct. 30, 1970 [21] Appl.No.: 85,560

[72] lnventor:

Primary Examiner0thell M. Simpson Attorney-James H. Phillips [57] ABSTRACT A lapidary machine adapted to produce cabochon shaped gem stones or the like; the machine having a powered rotary grinding wheel provided with a contoured in cross section annular grinding surface adapted to grind peripheries of cabochon shaped gem stones; a powered rotary dop holding shaft structure adapted rotatably to carry a dop supported gem stone in contact with said annular grinding surface; said shaft structure axially parallel to and laterally movable relative to the rotary axis of said grinding wheel, said shaft structure having a generally oval shaped cam thereon; a normally stationary idler roller having a periphery engagable by said cam and means for adjusting the position of the periphery of said idler roller in directions laterally relative to the rotary axis of said shaft structure in order to progressively cut peripheries of stones down and to produce cabochon shaped stones of various overall sizes.

11 Claims, 5 Drawing Figures PATENTEDJUU m2 3.673.742 sum 10! 4 INVENTOR SYRH.A.COLBAUGH ATTORNEY INVENTOR, SYRIL A. COLBAUGH ATTORNEY PATENTEDJUL 41m sum 3 or 4 PATENTEDJUL 4 m2 3 673 742 saw u or 4 INVENTOR. SYRIL A. COLBAUGH gmmw ATTORNEY LAPIDARY MACHINE Semiprecious gem stones known as cabochons are generally oval shaped and usually provided with a flat back for mounting them in sets of brooches or other jewelry items. The generally oval shaped cabochon gem stones have a contoured side opposite to the flat mounting side and heretofore great skill has been required to grind and form symmetrical cabochons. A typical method is to attach a gem stone to a dop for handling it relative to a grinding wheel which may or may not be contoured. The operator must grind the shape of the stone to produce the cabochon. Various templates have been used for establishing oval shapes and contours, however, many semiprecious gems have certain size and configuration which may or may not be suitable for producing a cabochon of a given size. Therefore, some cabochons are slightly larger than others and may be of slightly different oval shapes depending upon the availability of material in a piece of semiprecious gem stone. Accordingly, it is well known that considerable skill must be exercised in cutting a stone down to size in order to preserve the most attractive aesthetic configuration thereof and still frame such configuration in a symmetrical cabochon shape. It has been recognized that progressive grinding or cutting of such stones to a cabochon shape may proceed from a relatively large shape to a relatively smaller shape finally to attain a completely symmetrical and fault free cabochon.

Artisans who have guided the grinding of cabochons by hand spend a great deal of time and consequently such operations are relatively extensive. Additionally, the attainment of accurate symmetry has been considerably difficult when employing some manual and semi-manual methods.

In accordance with the present invention, a completely automatic grinding or cutting machine is utilized for producing cabochons of a given oval shape and contour while providing for progressive cutting of such stones from relatively large sizes to relatively small sizes in accordance with a simple dop holding shaft structure having an oval shaped cam thereon and an idler roller which the cam bears against and means for adjusting the idler roller laterally of the axis of the cabochon shaft supporting structure so as to permit a cabochon to be gradually ground to a finished shape and to be progressively cut or ground from a relatively large size to a relatively small size without departing from true cabochon symmetry. The machine of the invention employs carriage mechanism for a cabochon holding shaft structure which allows axial and lateral adjustment of the stone relative to the grinding wheel during the forming of a cabochon from a semiprecious gem stone.

The machine of the invention is provided with a cabochon or work piece holding shaft structure having a rotary axis movable laterally relative to a grinding wheel and carriage means rotatably supports the work piece holding shaft structure and movably mounts the shaft structure to move toward and away from the grinding wheel axially and laterally and an oval shaped cam carried by the shaft structure bears against an idler roller when the gem stone is in contact position relative to the grinding wheel so that during the rotation of the work piece holding shaft structure the cam operating against the idler roller moves the dop supported gem stone toward and away from the grinding wheel in an oval shaped pattern of movement and the idler roller is adjustable toward and away from the axis of the work piece holding shaft structure so as to cause the cam thereon to operate at variously spaced positions relative to the surface of the grinding wheel and to thereby permit progressive cutting or grinding of a semiprecious gem on the annular surface of the grinding wheel from a relatively large cabochon shape to a relatively small cabochon shape as desired.

Accordingly, it is an object of the invention to provide a fully automatic cabochon grinding machine which very rapidly and very accurately produces finished cabochons having very accurate symmetry.

Another object of the invention is to provide a machine having very simple cam mechanism which is adjustable for the purpose of progressively grinding a gem stone into a cabochon shape down to a relatively smaller cabochon shape as desired.

Another object of the present invention is to provide a cabochon grinding machine wherein a cam is used as a master oval shaped member while a semiprecious gem stone is being cut into a cabochon shape whereby very accurate and positive control of the cutting or grinding operation may be attained.

Another object of the invention is to provide a very delicate means of adjusting the bearing force of a gem stone being cut relative to the grinding wheel of the machine of the invention so as to attain the desired cutting rate and/or the finishing rate relative to operations thereon.

Another object of the invention is to provide a cabochon grinding machine which is very simple and easy to control in a precise manner to avoid over-grinding or over-cutting of stones and which thereby alleviates the possibility of accidentally damaging or ruining a valuable stone as may be the case when unskilled manual operations are relied upon.

Further objects and advantages of the invention may be apparent from the following specification, appended claims and accompanying drawings.

FIG. 1 is a perspective view of a cabochon grinding machine in accordance with the present invention and showing a cabochon carried on a dop holding shaft in connection with the work holding shaft structure of the invention and showing the stone in position relative to the periphery of a grinding wheel of the invention for being ground into a cabochon shape;

FIG. 2 is a top or plan view of the cabochon grinding machine of the invention showing the work piece holding shaft structure moved laterally of its axis to a position in which a work piece held by a dop in connection with the work piece holding shaft of the invention is moved away and out of contact relation with an annular grinding surface of a grinding wheel of the invention;

FIG. 3 is an enlarged fragmentary perspective view of the work piece holding shaft structure of the invention together with carriage means for moving it in two different directions relative to the grinding wheel of the invention;

FIG. 4 is an enlarged fragmentary sectional view taken from the line 44 of FIG. 1; and

FIG. 5 is an enlarged fragmentary sectional view taken from the line 55 of FIG. 4.

As shown in FIGS. 1 and 2 of the drawings, the invention comprises a tray shaped frame 10 which is preferably made of steel or other rigid material. This frame 10 is tray shaped having elevated side edge portions 12 to form a coolant receiving sump 14. This coolant receiving sump is adapted to catch coolant liquid which is introduced into the grinding wheel of the invention during operation as will be hereinafter described in detail.

The frame 10 is provided with an upstanding plate 16 to which a pillow block 18 is secured by bolts 20. Rotatably mounted in the pillow block 18 is a shaft 22 carrying a grinding wheel 24. Mounted on the shaft 22 is a drive pulley 26 engaged by a belt 28 which passes over a pulley 30 driven by an electric motor 32. This electric motor is carried by the frame 10 and is devoted to the driving of the grinding wheel 24 as will be hereinafter described. The grinding wheel 24 as shown in FIG. 1 of the drawings, is clamped to the shaft 22 by means of the usual flanged nut structure 32 screwthreaded on the end 34 of the shaft 22. This end being opposite to the end 22 which carries the pulley 26.

Mounted on the frame 10 by means of bolts or other suitable fixtures is a carriage mounting plate 36. Secured to this carriage mounting plate 36 is a pair of gib structures 38 and 40 in which the base 42 of a first carriage structure is slidably mounted in directions as indicated by a double ended arrow A in FIG. 1 of the drawings and as will be hereinafter described in detail.

The plate 42 carries a pair of upstanding plate structures 44 and 46 which are fixed to the plate 42.

Rotatably mounted between the plates 44 and 46 is a pivot shaft 48 on which a lower bearing portion 50 of a work holding shaft structure support 52 is mounted. Thus, the lower bearing structure 50 provides for pivotal mounting of the shaft support 52 on a horizontal axis which is generally parallel to the axis of the shaft 22.

The shaft support 52 is provided with an upper bearing portion 54 in which a work holding shaft structure 56 is rotatably mounted. Mounted on one end of the shaft structure 56 is a generally oval shaped model cam 58 and mounted on the opposite end of the shaft structure 56 is a conventional jaw chuck 60 adapted to hold a dop shaft 62 for mounting a semiprecious gem to be ground into a cabochon shape.

Secured to the work piece holding shaft structure adjacent to the jaw chuck is a pulley 64 engaged by a belt 66 driven by a pulley 68 in connection with the shaft of a motor 70, all as shown best in FIGS. 1 and 2 of the drawings. The motor 70 as shown in FIG. 2 of the drawings, is provided with a bracket 72 fixed to the support 52 so that the motor 70 is carried by the shaft support 52 and moves with the ing shaft structure 56.

The shaft structure 56 is provided with suitable axial thrust bearings in relation to the bearing portion 54 so that the shaft structure 56 is maintained or restrained in accurate axial disposition relative to the lower bearing 50 and the shaft 48 on which it is axially restrained by means of a set screw 74. Thus, the axis of the shaft structure 56 may pivot about the axis of the shaft 48 but may be maintained in a certain adjusted position wherein the shaft 56 is restrained against axial movement during the grinding of a cabochon carried by a dop shaft 62 in the jaw chuck 60.

As shown best in FIGS. 1 and 2 of the drawings, the carriage plate 42 may be slidably adjustably moved relative to the gibs 38 in a direction axially parallel to the axis of the work piece holding shaft structure 56 and this may be accomplished by an adjustment screw 76 operated by manually engaged wheel 78. The screw 76 is provided with a pair of collars 80 and 82 which are rotatably engaged with opposite sides of an upstanding bearing plate 84 fixed to the frame in connection with the plate 36. Thus, the screwthreaded adjustment shaft 76 is axially restrained against movement relative to the plate 36 but is screwthreaded in the upstanding plate 46 fixed to the carriage base plate 42. Thus, when the adjustment screw 76 is rotated by the manually operable wheel 78 the screwthreaded helical advancement of the plate 46 along the axis of the screw 76 causes the carriage plate 42 to slide in the gibs 38 and 40 and to move the work piece holding shaft structure 56 in a direction longitudinally along its axis for changing the axial position of the dop shaft 62 and a stone 64 relative to an annular grinding surface 66 of the grinding wheel 24 all as will be hereinafter described in detail.

As shown in FIGS. 1 and 2 of the drawings, the upstanding plate 46 carried by the carriage plate 42 supports a bracket 90 and bolts 92 secure this bracket 90 to the upstanding plate 46. The bracket 90 is provided with a fixed carriage supporting plate 94 having a pair of gib bearing straps 96 relative to which a carriage plate 98 is slidably mounted on the plate 94.

Carried by the plate 98 is a shaft 100 on which an idler roller 102 is rotatably mounted. Theaxis of this roller is sub stantially parallel to the axis of the work piece holding shaft structure 50 and is generally parallel to the axis of the grinding wheel 24.

An adjustment screw 104 is axially restrained by collars 106 relative to an upstanding plate 108 in connection with the plate 94 so that the adjustment screw 104 may be rotated by a hand wheel 110 and this adjustment screw 104 is screwthreaded into the plate 98 so as to move it relative to the plate 94 and the gibs 96 in a direction at substantially right angles to the axis of the shaft 100 and to thereby adjust the periphery of the idler wheel 102 toward and away from the axis of the work piece holding shaft structure 50 so that the model cam may be caused to control rotation and lateral cyclic movement about its axis for rotating and moving the work piece holding shaft structure toward and away from the contour surface 66 of the grinding wheel 24 during each rotative cycle of the shaft structure 56.

work piece or dop hold- Connected to the shaft supporting plate 52 is an externally screwthreaded arm 114 on which is screwthreadably mounted a counterweight member 116. The arm 114 extends away from the shaft support 56 in a cantilever manner and the counterweight 116 is screwthreadably and rotatably movable longitudinally along the cantilever arm 114 in order to provide a counterbalance for the weight of the motor 70 and to control the amount of force exerted between the stone 64 carried by the dop shaft 62 and the annular grinding surface 66 of the wheel 24.

Thus, the counterweight 1 16 may adjust the pivotalbalance of the shaft support 52 to thereby allow a certain portion of the weight of the motor 70 to cause a desired bearing pressure of the stone 64 against the annular-grinding surface 66 of the grinding wheel 24 during the grinding and/or cutting of the stone 64 to a desired cabochon shape of a desired size.

As shown in FIGS. 1 and 2 of the drawings, a shroud 118 partially covers the grinding wheel 24 and carries a liquid coolant inlet conduit 120 having a valve 122 adapted to shut off or control the flow ofi' coolant liquid onto the grinding wheel 24 internally of the shroud 118. This shroud 1 18 is provided with an open portion 124 through which the dop shaft 62 may pass when the stone or gem 64 is brought into contact with the annular grinding surface 66 of the grinding wheel 24.

As shown in FIGS. 4 and 5 of the drawings, the grinding wheel 24 carried on the shaft 22 is provided with an annular grinding surface 66 as hereinbefore pointed out. This annular grinding surface 66 is preferably provided with electroplated diamonds or other suitable abrasive material disposed in a contoured shape such as shown in cross section in FIG. 5 of the drawings, and this is a generally annular concave in cross section shape suitable for finishing the crown surface of cabochon shaped gem stones. As shown in FIG. 5, a gem stone 64 is partially ground and cut to shape in connection with a dop 63 on a dop shaft 62 carried in connection with the jaw chuck 60.

As shown in FIG. 4 of the drawings, it will be seen that the grinding wheel 24 and its shaft 22 rotate in the direction of an arrow B and that the dop shaft 62 and the work piece holding shaft structure 86 rotate in a direction as indicated by an arrow C resulting in an opposite peripheral relative movement of the annular grinding surface 66 and a peripheral portion 126 of the gem stone 64. As for example, the grinding wheel may operate at 4,000 rpm and may be six inches in overall diameter while the work piece holding shaft structure 56 may operate at 50 rpm. Accordingly, there is a cutting differential speed of 4,050 rpm and the work piece holding shaft structure 56 is concurrently rotated and moved toward and away from the annular grinding surface 66 in accordance with the contour shape of the model cam 58 bearing against the axially stationary idler roller 102. As a cutting operation begins, the idler roller 102 may be gradually backed away from the axis of the cam 58 and the work piece holding shaft structure 56 gradually to move it toward the annular grinding surface 66 of the grinding wheel 24. Accordingly, cabochon of various sizes may be accurately machined in relation to the general oval shape of the model cam 58 and these stones may be progressively ground from a larger size to a smaller size to reach an optimum finishing of the desired characteristics and features of the particular gem stone all as indicated at 64 in FIGS. 3 and 4 of the drawings.

It will be appreciated that the adjustable idler 102 provides means by which a stone may gradually be cut from a large size to a small size while maintaining accurate oval shaped configuration of the stone at all times during the progression in cutting and grinding from a larger size to a smaller size so that finished grinding may be accomplished at any desirable size. When the counterweight 116 is adjusted so as to permit pivotal movement of the shaft support 52 toward the grinding wheel periphery 66 the model cam 58 constantly follows the position of the periphery of the idler 102 and when the position of this idler 102 is changed the lateral axial disposition of the work piece holding shaft structure 56 changes accordingly.

It will be obvious to those skilled in the art that various modifications of the invention may be resorted to without departing from the spirit thereof.

I claim:

1. In a lapidary machine, the combination of: a frame; a power driven grinding wheel rotatably mounted thereon; said grinding wheel having a concave surface extending from, respectively, spaced points on the radial and peripheral faces of said wheel; a dop holding shaft structure having one end adapted to carry a dop and a stone thereon to be ground on said annular grinding surface; said dop holding shaft structure carrying a model cam; first means rotatably and movably mounting said dop holding shaft structure on said frame to move laterally relative to a rotary axis of said shaft structure and generally toward and away from said concave grinding surface; an idler roller engagable by said model cam; second means mounted on said frame and adjustably supporting said idler roller so as to move said idler roller in directions generally laterally relative to the axis of said shaft structure and toward and away from said model cam; power operated means for rotatably driving said shaft structure; and third means adapted for adjustably moving said first means in a direction parallel to the axis of said shaft structure and for moving it generally toward and away from said concave grinding surface and relative to said frame.

2. The invention as defined in claim 1 wherein said first means is pivoted on said frame on an axis disposed laterally relative to the axis of said shaft structure, said power operated means being carried by said first means.

3. The invention as defined in claim 2 wherein an elongated cantilever counterbalance arm is carried by said first means, said arm extending generally in a direction laterally relative to said axis about which said first means is pivoted on said frame; and a counterbalance weight adjustably movable longitudinally along said arm.

4. The invention as defined in claim 1 wherein said shaft structure is provided with an adjustable jaw chuck adapted to hold a dop supporting shaft at said one end.

5. The invention as defined in claim 1 wherein said frame comprises a pan-shaped tray; and conduit means for directing liquid coolant material onto said concave grinding surface; and shroud means partially surrounding said grinding wheel.

6. The invention as defined in claim 5 wherein said shroud means is provided with an opening therein adapted to permit a dop shaft, at one end of said shaft structure, to pass through said opening to carry a stone, to be cut, into said shroud means and into contact with said concave grinding surface.

7. The invention as defined in claim 1 wherein a first carriage supports said first means and said idler and said second means, said first carriage means movable on said frame to carry said dop holding shaft structure and said idler roller together with said second means in directions toward and away from said grinding wheel and said directions being generally parallel to the rotary axis of said dop holding shaft structure.

8. The invention as defined in claim 7 wherein a screwthreaded shaft means is rotatably mounted on said frame and restrained axially relative thereto, said first carriage having an internally screwthreaded means conformingly engagable by said threaded shaft means whereby rotation of said threaded shaft means causes said carriage to be moved relative to said frame in said directions.

9. The invention as defined in claim 7 wherein said second means comprises a second carriage movably mounted on said first carriage; said second carriage movable relative to said first carriage in directions toward and away from said dop holding shaft structure and at an angle to the axis thereof.

10. The invention as defined in claim 3 wherein said counterbalance weight is screwthreadably coupled to said arm for adjustment relative thereto and longitudinally therealong.

11. The invention as defined in claim 7 wherein said first means is provided with a lower bearing portion pivotally mounted on said first carriage; said first means having an upper bearing portion spaced laterallyfrom said lower bearing portion and said upper bearing portion rotatably mounting said dop holding shaft structure about its rotary axis, said lower bearing portion having a pivotal axis generally parallel to said upper bearing portion. 

1. In a lapidary machine, the combination of: a frame; a power driven grinding wheel rotatably mounted thereon; said grinding wheel having a concave surface extending from, respectively, spaced points on the radial and peripheral faces of said wheel; a dop holding shaft structure having one end adapted to carry a dop and a stone thereon to be ground on said annular grinding surface; said dop holding shaft structure carrying a model cam; first means rotatably and movably mounting said dop holding shaft structure on said frame to move laterally relative to a rotary axis of said shaft structure and generally toward and away from said concave grinding surface; an idler roller engagable by said model cam; second means mounted on said frame and adjustably supporting said idler roller so as to move said idler roller in directions generally laterally relative to the axis of said shaft structure and toward and away from said model cam; power operated means for rotatably driving said shaft structure; and third means adapted for adjustably moving said first means in a direction parallel to the axis of said shaft structure and for moving it generally toward and away from said concave grinding surface and relative to said frame.
 2. The invention as defined in claim 1 wherein said first means is pivoted on said frame on an axis disposed laterally relative to the axis of said shaft structure, said power opErated means being carried by said first means.
 3. The invention as defined in claim 2 wherein an elongated cantilever counterbalance arm is carried by said first means, said arm extending generally in a direction laterally relative to said axis about which said first means is pivoted on said frame; and a counterbalance weight adjustably movable longitudinally along said arm.
 4. The invention as defined in claim 1 wherein said shaft structure is provided with an adjustable jaw chuck adapted to hold a dop supporting shaft at said one end.
 5. The invention as defined in claim 1 wherein said frame comprises a pan-shaped tray; and conduit means for directing liquid coolant material onto said concave grinding surface; and shroud means partially surrounding said grinding wheel.
 6. The invention as defined in claim 5 wherein said shroud means is provided with an opening therein adapted to permit a dop shaft, at one end of said shaft structure, to pass through said opening to carry a stone, to be cut, into said shroud means and into contact with said concave grinding surface.
 7. The invention as defined in claim 1 wherein a first carriage supports said first means and said idler and said second means, said first carriage means movable on said frame to carry said dop holding shaft structure and said idler roller together with said second means in directions toward and away from said grinding wheel and said directions being generally parallel to the rotary axis of said dop holding shaft structure.
 8. The invention as defined in claim 7 wherein a screwthreaded shaft means is rotatably mounted on said frame and restrained axially relative thereto, said first carriage having an internally screwthreaded means conformingly engagable by said threaded shaft means whereby rotation of said threaded shaft means causes said carriage to be moved relative to said frame in said directions.
 9. The invention as defined in claim 7 wherein said second means comprises a second carriage movably mounted on said first carriage; said second carriage movable relative to said first carriage in directions toward and away from said dop holding shaft structure and at an angle to the axis thereof.
 10. The invention as defined in claim 3 wherein said counterbalance weight is screwthreadably coupled to said arm for adjustment relative thereto and longitudinally therealong.
 11. The invention as defined in claim 7 wherein said first means is provided with a lower bearing portion pivotally mounted on said first carriage; said first means having an upper bearing portion spaced laterally from said lower bearing portion and said upper bearing portion rotatably mounting said dop holding shaft structure about its rotary axis, said lower bearing portion having a pivotal axis generally parallel to said upper bearing portion. 